Apparatus of that type is known from Document EP 0 627 335 which shows a hydrostatic transmission vehicle having a plurality of axles, two pumps feeding respective ones of the motors that drive the wheels on each of the two sides of the vehicle. That apparatus offers the advantage of adjusting the respective cylinder capacities of the two pumps in identical manner for travelling straight ahead, or in different manners when, for example, to make a tight turn, it is necessary for the motors driving the wheels on one side of the vehicle to deliver torque that is higher than the torque delivered by the motors driving the wheels on the other side.
Thus, the apparatus disclosed by Document EP 0 627 335 makes it possible to obtain a behavior that differs between the wheels on one side of the vehicle and the wheels on the other side. Unfortunately, it does not make it possible to manage differences in behavior between the wheels situated on the same side of the vehicle.
Document EP 0 547 947 also discloses a vehicle having hydrostatic transmission including three-port dual-capacity motors. All of the motors are fed by the same pump, and it is possible to avoid undesirable differences in behavior between the wheels of the various axles, e.g. wheel spin. Thus, it is possible to achieve a differential lock effect between the front axle and the rear axle, but not to manage in different manners the feed to the motors driving the wheels on one side or the other of the vehicle.
The above-mentioned known apparatus thus offers certain advantages which unfortunately have corresponding drawbacks that are problematic to various extents depending on the conditions under which the vehicle is used.